Anti-Markovnikov hydro- and deuterochlorination of unsaturated hydrocarbons using iron photocatalysis

Abstract

The hydrochlorination of unsaturated hydrocarbons is a fundamental reaction in organic synthesis. Traditional acid-mediated approaches proceed with Markovnikov selectivity, but direct access to anti-Markovnikov hydrochlorination products is still a longstanding pursuit. Previous methods are restricted by the need for multiple synthetic steps, stoichiometric chlorine and hydride sources and/or highly oxidative photocatalysis, resulting in limited scope and, in some cases, low regioselectivity. So, the development of redox-neutral hydrochlorination with high anti-Markovnikov regioselectivity compatible with both alkenes and alkynes remains important. Here we report a photocatalytic anti-Markovnikov hydro- and deuterochlorination of unsaturated hydrocarbons enabling access to diverse alkyl and alkenyl chlorides regio- and stereoselectively. Broad scope (125 examples), mild conditions and regio- and isotopo-divergent syntheses are demonstrated. Key to this method is the combination use of ligand-to-metal charge transfer photoreactivity of earth-abundant iron and hydrogen atom transfer reactivity of redox-active thiol. This cooperative system offers a powerful strategy for anti-Markovnikov hydrofunctionalization of unsaturated hydrocarbons. Methods for the anti-Markovnikov-selective hydrochlorination of unsaturated C–C bonds are limited by the need for stoichiometric reagents, highly oxidizing photocatalysts and multiple synthetic steps. Now the combination of ligand-to-metal charge transfer and hydrogen atom transfer reactivity enables the anti-Markovnikov-selective hydro- and deuterochlorination of unsaturated hydrocarbons using iron photocatalysis.